1. Field of the Invention
The present invention relates to an oil field tool which has been improved for a particular application in the oil field environment, where it is commonly referred to as a xe2x80x9cdownholexe2x80x9d motor. More specifically, a hydraulic motor of the tool incorporates a novel stator sleeve and guide bearings which eliminate distortion of the material thereof due to effects of the working environment when the tool is used within the shaft of a well, eliminating seizure of the motor during such use.
2. Prior Art
Heretofore the motor of the oil field tool has included a stator having a rubber sleeve therein within which a rotatable shaft called a rotor rotates, and guide bearings incorporating a rubber material insert therein for guiding a rotating drive shaft of a mill which is driven by the rotor. When such tool is used within a well shaft, because temperatures therein may reach almost 400xc2x0 F., the rubber of the sleeve and bearings inherently deforms, swelling against and around the rotating structures therewithin, causing the motor to seize.
Also, at times, the sleeve and bearings are simultaneously subjected to extremely low temperatures and chemical reactants, such as, for example, when liquid nitrogen is pumped through the tool for use in causing ejection of material blocking a well, such as a paraffin buildup which is broken apart by the tool, via the well shaft, with the rubber swelling further under these conditions by impregnation of the nitrogen thereinto.
Further, during repair of such seized motor, such a degree of pressure is needed to release a shaft from its entrapment within the rubber, that the shaft is often bent, requiring the purchase of a new shaft, each such shaft having a replacement price of $1500.00 or more.
Thus, there exists a need for bearings and a stator sleeve for the motor which will not be affected by ambient conditions of the working environment.
Accordingly, it is a primary object of the invention to provide an improved oil field tool which will not seize when subjected to ambient conditions of use within the shaft of a well.
This object, as well as others, is met by the oil field tool of the present invention wherein an inner sleeve of a stator and an insert of guide bearings for a mill drive shaft of the tool motor are made of a material such as a polymer which is not compromised in its chemical or physical characteristics over a temperature range of approximately 800xc2x0 F., or by contact thereof with liquid nitrogen.